Allergy Patch Testing for Eczema
This clinic is run by a team of doctors and nurses led by dermatology consultant Dr Nick Levell and Senior Staff Nurse Sarah Catten
This form of allergy testing is usually for eczema or dermatitis (two words for the same thing!) limited to a localised area. It is used for testing for allergies to things which may have touched the skin. It is not very helpful as a test for food allergies.
Patch testing does not involve needles. The photograph shows a close up of the tapes which are applied to the skin.
To read some information sheets on contact allergies click on: British Contact Dermatitis Society then click on “downloads” and “patient information leaflets”. These sheets give details of the things we test to and where people can come into contact with them.
What does patch testing involve?
Usually 40-100 chemicals are applied, using sticky tape, to the back on Monday. Patients then come back to the clinic to have readings twice, on Wednesday and Friday.
Sometimes we shine ultraviolet light onto the skin on Wednesday, 48 hours after appying the chemical. This is done if it is suspected that the allergy may be triggered by sunlight.
In 2009 we introduced a new computer database for recording the results which we hope will allow us to improve the relevance of the tests.
Does it hurt?
There are no needles involved. But it can feel rather unpleasant having sticky tape all over the back for a few days. A strong reaction can be very itchy. Men with hairy backs usually find removal of the tape rather uncomfortable.
What should I do or not do?
Don’t wash the back or do vigorous exercise when you are having the treatment (from Monday to Friday) or the tapes will fall off. If you have had much sun on the back within 2 weeks the reactions are usually supressed. We use a marker pen on the back so wear an old shirt or vest and not your best silk top!
What sort of chemicals are used?
We use the sort of chemicals that people commonly come into contact with every day for example through touching coins, rubber gloves, clothes, shoes, newspaper, soaps, shampoos, make-up, household cleansers, plants, glues and items at work.
Can I bring things to test?
If there is something you are suspicious of then bring it along on the Monday. Some things such as strong detergents and corrosive chemicals can’t safely be tested but we have tested everything from bedroom toys to dog saliva. Many people bring their shampoo and skin cleansing products to test.
Can anyone not be tested?
It isn’t really fair to test young children who don’t understand the need to have sticky tape all over their back for a few days. High doses of steroid tablets prevent the patches reacting. Excessive sun exposure on the back can also prevent the patches reacting for two weeks afterwards. We don’t test people who are pregnant or breast feeding.
Does patch testing identify allergies due to food, medicines, things in the air and bee stings?
No. Other mechanisms in the body can cause these allergies and these are tested for in other ways in the Dermatology Allergy Clinic